Compressor



Dec. 23, 1 4 1,520,255

L. A. MAXSON COMPRESSOR Original Filed 001:. a, 1921 Patented Dec. 23, 1924.

LOUIS A. MAXSON, OF CLAREMON'T, NEW HAMPSHIRE, ASSIGNOR 'I'O SULLIVAN MACHINERY COMPANY, A CORPORATION OF MASSACHUSETTS.

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Application filed October 8, 1921, Serial No. 506,384. Renewed September 6, 19%.

To all whomit may concern:

Be it known that I, LOUIS A. MAXSON, a citizen of the United States, residing at Claremont, 'in the county of Sullivan and 6 State of New Hampshire, have invented certain new and useful Improvements in Compressors, of which the following is a full, clear, and exact specification.

My invention relates to compressors and more especially to unloading systems for compressors.

It has for its object to provide an improved meohanism cooperating with the compressor in a new and improved manner whereby the same may be automatically unloaded or loaded as conditions vary. A more specific object of my invention is to provide improved controlling mechanism especially adapted to multi-stage compressors wherein one set of inlet valves, as for instance, those of the low pressure cylinder, are actuated to unload the compressor and wherein another set of inlet valves as for instance those of the high pressure cylinder, are subsequently actuated to complete the unloading of the compressor, these last mentioned valves being controlled by improved means automatically responsive to the vari- 'ations in pressure resulting from unloading the low pressure cylinder. A further object of my invention isto provide an improved type of unloading mechanism adapted to cooperate with either the valves of the high or low pressure cylinders and by reason of its particular construction automaticall producing the desired delay between the unio'ading of the respective cylinders. These and other objects of my invention will, however, hereinafter more fullyv appear.

In the accompanyig drawings I have shown for purposes of illustration my invention as applied to a two-stage compressor, although it will be readily understood that the same is not limited to a machine of the particular construction shown.

In these drawings,-

Fig. 1 is a partial side elevation of the compressor equipped with the illustrative form of my improvement.

Fig. 2 is a partial side elevation of a compressor provided as to one stage thereof with my improved type of inlet valve actuating mechanism hereinafter described, the compressor, however, being unloaded as to the low pressure cylinder by intake closing means.

Fig. 3 is a central vertical section on an enlarged scale through a fragmentary portion of the intake chamber and one head of a compressor cylinder showing my improved mechanism in position.

In this illustrative construction I have shown a compressor 1 mounted upona suitable base 2 and having low and high pressure cylinders 3 and 4 in which are movable pistons (not shown) in a well-known manner, the operating means for these pistons not being illustrated as the construction is well known in the art. Connecting the cylinders 3 and 4 is an intercooler 5 and a pipe 6 leads from the discharge chest of the high pressure cylinder 4 to a receiver 7. For the purpose of unloading the compressor, I employ an unloading system resembling in some features that disclosed in the application of one Fred D. Holdsworth, Serial No. 134,452, filed November 28, 1916, and comprising a connection 8 leading to a pilot valve 9, herein of the well known Judson type illustrated in Patent No. 1,141,975, granted to one John L. Osborne on June 8, 1915., The pilot valve 9 controls the supply of air through the pipe 8 from the receiver to branch passages 10 and 11 which lead to Ts 12 and 13, respectively, and from these Ts air admitted through the pilot valves is led to means cooperating with the inlet valves of the high and low pressure cylinders respectively, and generally designated 14-, these means constituting per se and in combination with the remainder of the structure disclosed, my invention.

Considering the form of the same shown in Fig. 3 it will be noted that the cylinder shown therein-is provided with the usual inlet valve 15 having a stem 16 connected thereto and provided with a collar 17 ar ranged at the opposite end of the stem, which collar is engaged by a spring 18 abutting against a flange 19 formed on the stem guide 20 in the valve. cage member 21. The construction as so far described is of familiar construction. Cooperating with this mechanism is an improved mechanism e comprising a housing 22 having herein cylinders of differential bores 23 and 24, respectively, formed herein in alinement and communicating with each other. Within the cylinders 23 and 24 is reciprocable a com- 1o pound piston comprising a large head 25 fitting the larger cylinder 23' and a small head 26 fitting the smaller bore 24:. The compound piston is provided with a stem 28 adapted to engage the collar 17 or the end of the stem 16 and, upon upward movement of the pistons, unseat the inlet valves and maintain them unseated. It will be noted that the upper surface of the larger piston 25 is exposed to the pressure in the intake chamber of the cylinder towhich it is attached and accordingly that dependent upon the pressure existing in the intake chamber, upon the relative areas of the pistons and 26, and upon the pressure acting upon the 25 end of the smaller piston 26, the delay in operation between the moment of admission of pressure beneath the piston 26 and the upward movement of the compound piston will be variable. It will be clear that this so mechanism can be connected to the lowpressure cylinders and that due to the fact that the pressure in the, intake is atmospheric pressure only, as soon as the pilot valve 9 operates, the compound pistons will be 8 moved upward and unload the low pressure cylinder by opening the inlet valves thereof.

In the case of the highpressure cylinder, however, the pressure which is admitted [through the branch pipe 10 simultaneously with the admission of pressure through the pipe .11 to the low pressure unloading mechanism, will not be able to raise the pistons and open the inlet valves due to the fact that intercooler pressure may be in the case of the compound compressor, say fifty pounds, and this pressure acting upon the piston 25, upon an area, for example, ten times that of the area exposed to receiver pressure will easily keep the high pressure cylinder loaded and actively pumping down intercooler pressure until that pressure has been pumped down to say ten pounds if receiver pressure is slightly above one hundred pounds. It will thus be evident that a considerable delay will be inserted between the respective unloadings of the high and low pressure cylinders and that a single mechanism identical in construction may be employed with the inlet valves of the respective cylinders and will automatically by reason of its construction and cooperation with the inherent peculiarities of the phenomena in the intake chambers of the several cylinders, operate in the desired manner. It will be observed that the parts 23, 24, 25, 26, etc., constitute valve controlling servo-motors.

It will be clear that instead of the mechanism as shown in Fig. 1, a mechanism of the intake closure type could be employed upon the low pressure cylinder as shown in Fig. 2 of the accompanying drawings and the cooperation of my improved mechanism with the high pressure cylinder would be the same in either case. It will also be understood that in practice the pistons 25 and 26 will be packed with cup leathers or otherwise arranged to prevent leakage and that the relative areas of the pistons will be varied to suit the conditions and resultsdesired, even being made the same in some cases and with some types of pilot valves. It will be evident also that but one form of valve control mechanism need be made up and that the single mechanism can be used Without change either on high or low pressure cylinders.

While I have in this application specifically described and shown one form which my invention may assume in practice, it will be understood that this form is shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claimas new and desire to secure by Letters Patent is:

1. Unloading means for multistage compressors comprising means for opening the inlet valves of the cylinders of each stage including fluid pressure controlled pistons subjected continuously on one side to the pressure at the intake side of the cylinder with whose inlet valves it cooperates, and on the other side intermittently and in accordance with discharge pressure variations to fluid pressure at higher pressure, said pistons presenting substantially different areas to such intake and higher pressures, the areas at the opposite sides of one of said pistons being such that the force opposing movement thereof during normal compressor running exceeds the force tending to move it resulting from the action thereon of said higher pressure.

2. Means for unloading a compressor by opening the inlet valves thereof comprising a differential cylinder, a differential piston reciprocable therein, means for subjecting one side of said piston continuously to the pressure in the intake chamber of the cylinder with which it is used, and means for intermittently subjecting the other side thereof to compressor discharge pressure, the ratio of the area of the side subject to the pressure in the intake chamber'to the area subjected to compressor discharge pressure being greater than the ratio of compressor discharge pressure to the pressure in said intake chamber during normal loaded runmn '3. Means for actuating the inlet valves of a compressor comprising coaxially arranged cylinders in alinement with said valves, oppositely acting pistons in said 0 linders, means for subjecting one of said pistons to compressor discharge pressure in excess of a predetermined desired maximum to open said inlet valves, and means for subjecting the other of said pistons to the pressure in the intake chambers of the cylinder whose valve it controls, the product of. the area of said first mentioned piston multiplied by compressor discharge pressure being less than the product of the area of said second mentioned piston multiplied by the pressure in the intake chamber of the cylinder whose valve it controls at a time when the compressor is running normally loaded.

4. Means for unloading both cylinders of a compound compressor comprising identical means for opening the inlet valves of each of said cylinders, each of said means being subjected to the same pressure to cause opening of said valves, and to the pressures in the intakes of their respective cylinders to' oppose opening, said means presenting different areas to said opening and oppos- 1ng pressures.

5. Means for opening the inlet valves of a compressor to unload the latter including a cylinder containing member having alined bores of difierent diameters and disposed in alinement with said inlet valves, a multiple iston having portions fitting each of said ores, means for subjecting the smaller of said pistons to receiver pressure to open said valves, and means for connecting the opposite surface of the larger of said pistons to pressure in the intake of its associated com- I pressor cylinder, said means being identical for the several cylinders of multistage compressors and operating to delay the unloading of succeeding cylinders after the unloading of the low pressure stage. i

6. Unloading means for multistage com-' pressors including identical servo-motors for each cylinder thereof, and means for supplying operating medium to each of said motors to cause the same to unload their respective cylinders, said motors automatically causing the low pressure cylinder to unload first. g

7. Means for unloading a compressor by openingthe inlet valves thereof comprising a cylinder, a piston reciprocable therein, means for intermittently subjecting one side of said piston to a pressure adapted to move the same in a direction to efiect compressor unloading, and means for opposing the unloading of the compressor by movement of said piston exercising a force greater than the force produced by the action of pressure 7 tively large area at one side of said movable 4 member to the pressure in the intake chamber of the cylinder with which it is used,

and means for intermittently subjecting a smaller area at the other side of said mem ber to compressor discharge pressure.

9. Means for unloading both cylinders of a compound compressor comprising identical difierential pistons for opening the valves of each of the cylinders, each of said pistons being subjected to the same pressure to cause opening of the valves and during the loaded running of the compressor to unequal pressures.

10. Means for unloading both cylinders of a compound' compressor. comprising means associated with each cylinder and operative on actuation .to effect unloading 7 thereof, means for actuating said unloading means comprising members adapted to be moved by receiver pressure to efl'ect such actuation and to which receiver pressure is simultaneously admissible when unloadin is to occur, and means associated with said members for initially unequally opposing their movements to cause them to become effective at diflerent times.

11. Means for unloading both cylinders of a compound compressor, comprising means associated with each cylinder and operative on actuation to effect unloading thereof,

means for actuating said unloading means comprising members adapted to be .movedby receiver pressure to effect such actuation and to which receiver pressure is simultaneously admissible when unloading is to occur, and fluid pressure operated means associated with said members for initially unequally opposing their movements to cause them to become effective at substantially difierent'times.

12. Unloading means for multistage compressors comprising means for opening the inlet valves of the cylinders of each stage including identical fluid pressure controlled differential pistons subjected continuously on one side to the pressure at the intake side of the cylinder with whose inlet valves it cooperates, and on the other side intermittently and in accordance with discharge pressure variations to fluid pressure at higher pressure.

13. Unloading means for multistage compressors comprising means for opening the other side intermittently and in accordance inlet valves of the cylinders of each stage With discharge pressure variations to fluid including fluid pressure controlled pistons pressure at higher pressure, said last men- 10 having unequal oppositely acting areas subtioned side being the smaller. jected continuously on one side to the pres- In testimony whereof I aflix my signasure at the intake side of the cylinder with ture.

Whose inlet valves it cooperates, and on the LOUIS A. MAXSON 

